Aerosol Generating System with Prevention of Condensate Leakage

ABSTRACT

There is provided an aerosol generating system for heating a liquid aerosol-forming substrate. The system includes an aerosol-forming chamber, and a leakage preventer for preventing or reducing leakage of liquid aerosol condensate from the aerosol generating system. The leakage preventer may include one or more of: at least one cavity in a wall of the aerosol-forming chamber, for collecting droplets of condensed liquid aerosol-forming substrate; at least one hooked member for collecting droplets of condensed liquid aerosol-forming substrate; an impactor for disrupting airflow in the aerosol-forming chamber so as to collect liquid droplets; and a closure member for substantially sealing the aerosol-forming chamber when the aerosol generating system is not in use.

The present invention relates to an aerosol generating system. Inparticular, the present invention relates to an aerosol generatingsystem in which the aerosol-forming substrate is liquid.

WO-A-2009/132793 discloses an electrically heated smoking system. Aliquid is stored in a liquid storage portion, and a capillary wick has afirst end which extends into the liquid storage portion for contact withthe liquid therein, and a second end which extends out of the liquidstorage portion. A heating element heats the second end of the capillarywick. The heating element is in the form of a spirally wound electricheating element in electrical connection with a power supply, andsurrounding the second end of the capillary wick. In use, the heatingelement may be activated by the user to switch on the power supply.Suction on a mouthpiece by the user causes air to be drawn into theelectrically heated smoking system over the capillary wick and heatingelement and subsequently into the mouth of the user.

The aerosol generating systems of the prior art, including theelectrically operated smoking system referred to above, do have a numberof advantages, but there is still opportunity for improvement in thedesign.

According to a first aspect of the invention, there is provided anaerosol generating system for heating a liquid aerosol-formingsubstrate, the system comprising: an aerosol-forming chamber; andleakage prevention means configured to prevent or reduce leakage ofliquid aerosol condensate from the aerosol generating system.

The aerosol generating system is arranged to vaporize the liquidaerosol-forming substrate to form a vapour, which condenses in theaerosol-forming chamber to form the aerosol. Thus, the aerosol-formingchamber simply assists or facilitates the generation of the aerosol. Theaerosol generating system may include the aerosol-forming substrate ormay be adapted to receive the aerosol-forming substrate. As known tothose skilled in the art, an aerosol is a suspension of solid particlesor liquid droplets in a gas, such as air.

An advantage of the invention is that leakage of liquid aerosolcondensate from the aerosol generating system is prevented or at leastsubstantially reduced. The condensed liquid (liquid condensate) may formdue to a change in temperature, for example a sudden temperature drop.Alternatively or additionally, the liquid condensate may accumulate incavities, grooves, corners or other portions of the aerosol generatingsystem where there is reduced airflow. The rate of condensation isaffected by the vapour pressure of the aerosol-forming substrate, thetemperature gradient between the vapour and the housing or wall of theaerosol generating system, and other factors, for example the airflowand turbulence. Minimising, or preferably preventing, leakage of theliquid aerosol condensate is important to avoid wastage of the liquidaerosol-forming substrate. In addition, if liquid leaks out of theaerosol generating system, this may cause inconvenience for the user.For example, the aerosol generating system may become wet or sticky.

The liquid aerosol-forming substrate preferably has physical properties,for example boiling point and vapour pressure, suitable for use in theaerosol generating system. If the boiling point is too high, it may notbe possible to vaporize the liquid but, if the boiling point is too low,the liquid may vaporize too readily. The liquid preferably comprises atobacco-containing material comprising volatile tobacco flavourcompounds which are released from the liquid upon heating.Alternatively, or in addition, the liquid may comprise a non-tobaccomaterial. The liquid may include water, solvents, ethanol, plantextracts, nicotine solutions and natural or artificial flavours.Preferably, the liquid further comprises an aerosol former. Examples ofsuitable aerosol formers are glycerine and propylene glycol.

In a first embodiment of the invention, the leakage prevention meanscomprises at least one cavity in a wall of the aerosol-forming chamber,for collecting liquid condensate formed from the aerosol-formingsubstrate.

Providing at least one cavity in a wall of the aerosol-forming chamberallows condensed droplets of the liquid to be collected. Preferably, theat least one cavity interrupts the flow route for droplets of condensedliquid which may otherwise leak out of the aerosol generating system.Thus, leakage of condensed liquid from the aerosol generating system isprevented or at least reduced. The at least one cavity may have anysuitable size and shape and may be located at any suitable location inthe aerosol-forming chamber. Preferably, the at least one cavity isclose to an outlet end of the aerosol generating system. If the aerosolgenerating system includes a liquid storage portion or a capillary wickor both a liquid storage portion and a capillary wick, the at least onecavity may comprise a return path for returning condensed liquiddroplets to the liquid storage portion or capillary wick.

In the first embodiment of the invention, the at least one cavity maycontain capillary material. Providing capillary material in the at leastone cavity minimises the free liquid. This reduces the likelihood thatcondensed liquid will leak from the aerosol generating system. Thecapillary material may comprise any suitable material or combination ofmaterials which is able to retain the collected liquid. The particularpreferred material or materials will depend on the physical propertiesof the liquid aerosol-forming substrate. Examples of suitable materialsare a sponge or foam material, ceramic- or graphite-based materials inthe form of fibres or sintered powders, a foamed metal or plasticsmaterial, a fibrous material, for example made of spinned or extrudedfibres, such as cellulose acetate, polyester, or bonded polyolefin,polyethylene, terylene or polypropylene fibres, nylon fibres or ceramic.Most preferably, the capillary material substantially fills the cavitiesso as to minimise the free liquid.

If the aerosol generating system includes a liquid storage portion or acapillary wick or both a liquid storage portion and a capillary wick,the capillary material may provide a return path for returning condensedliquid droplets to the liquid storage portion or capillary wick. Thecapillary material may be in contact with the capillary wick. Thecapillary material in the at least one cavity and the capillary wick maycomprise the same material or different materials.

In a second embodiment of the invention, the leakage prevention meanscomprises at least one hooked member for collecting droplets of liquidcondensate formed from the aerosol-forming substrate.

Providing a hooked member allows condensed droplets of the liquidaerosol-forming substrate to be collected. Preferably, the at least onehooked member interrupts the flow route for droplets of condensedliquid. Thus, leakage of liquid condensate from the aerosol generatingsystem is prevented. The at least one hooked member may have anysuitable size and shape and may be located at any suitable location. Forexample, the hooked member may be positioned on a wall of theaerosol-forming chamber.

In the second embodiment of the invention, the at least one hookedmember may comprise a recycle path for recycling the collected dropletsof the liquid condensate. The recycle path may comprise an angledportion of the hooked member. If the aerosol generating system includesa liquid storage portion or a capillary wick or both a liquid storageportion and a capillary wick, the recycle path may return condensedliquid droplets to the liquid storage portion or capillary wick. Thetrapping and transportation of condensate droplets can be enhanced bysurface properties (for example, but not limited to, surface profile,surface roughness) or material (for example, but not limited to, use ofa hydrophobic or hydrophilic material) of an inner wall of the aerosolgenerating system, for example the inner wall of the aerosol-formingchamber.

In the second embodiment of the invention, the at least one hookedmember includes capillary material. The capillary material may beprovided on part or all of the collecting surface of the hooked member.Providing capillary material on the at least one hooked member minimisesthe free liquid. This reduces the likelihood that condensed liquid willleak from the aerosol generating system. The capillary material maycomprise any suitable material or combination of materials which is ableto retain the collected liquid. The particular preferred material ormaterials will depend on the physical properties of the liquidaerosol-forming substrate. Examples of suitable materials are a spongeor foam material, ceramic- or graphite-based materials in the form offibres or sintered powders, a foamed metal or plastics material, afibrous material, for example made of spinned or extruded fibres, suchas cellulose acetate, polyester, or bonded polyolefin, polyethylene,terylene or polypropylene fibres, nylon fibres or ceramic.

If the hooked member includes a recycle path, preferably, the recyclepath includes the capillary material. This improves recycling of thecondensed liquid droplets. If the aerosol generating system includes aliquid storage portion or a capillary wick or both a liquid storageportion and a capillary wick, the capillary material may returncondensed liquid droplets to the liquid storage portion or capillarywick. The capillary material may be in contact with the capillary wick.The capillary material on the at least one hooked member and thecapillary wick may comprise the same material or different materials.

In a third embodiment of the invention, the leakage prevention meanscomprises an impactor for disrupting airflow in the aerosol-formingchamber so as to collect droplets of liquid being formed from theaerosol-forming substrate.

Providing an impactor which disrupts the airflow allows droplets of theliquid aerosol-forming substrate to be collected. This is because, asthe airflow is disrupted, some liquid droplets cannot be carried in theairflow and impact on the impactor instead. The collected liquiddroplets tend to be the larger liquid droplets. The collected liquiddroplets cannot leak out of the aerosol generating system. Thus, leakageof liquid condensate from the aerosol generating system is prevented.The impactor may have any suitable size and shape and may be located atany point downstream of the vapour formation.

In the third embodiment of the invention, the impactor may includecapillary material. The capillary material is preferably provided onpart or all of the upstream surface of the impactor. The capillarymaterial may be provided on other surfaces of the impactor. Providingcapillary material on the collecting surface of the impactor minimisesthe free liquid. This reduces the likelihood that liquid condensate willleak from the aerosol generating system. The capillary material maycomprise any suitable material or combination of materials which is ableto retain the collected liquid. The particular preferred material ormaterials will depend on the physical properties of the liquidaerosol-forming substrate. Examples of suitable materials are a spongeor foam material, ceramic- or graphite-based materials in the form offibres or sintered powders, a foamed metal or plastics material, afibrous material, for example made of spinned or extruded fibres, suchas cellulose acetate, polyester, or bonded polyolefin, polyethylene,terylene or polypropylene fibres, nylon fibres or ceramic.

If the aerosol generating system includes a liquid storage portion or acapillary wick or both a liquid storage portion and a capillary wick,the capillary material on the impactor may return liquid droplets to theliquid storage portion or capillary wick. The capillary material on theimpactor may be in contact with the capillary wick. The capillarymaterial on the impactor and the capillary wick may comprise the samematerial or different materials.

In a fourth embodiment of the invention, the leakage prevention meanscomprises a closure member for substantially sealing the aerosol-formingchamber when the aerosol generating system is not in use.

Providing a closure member which substantially seals the aerosol-formingchamber when the aerosol generating system is not in use substantiallyprevents any condensed liquid droplets from leaking out of the aerosolgenerating system when it is not in use. It should be understood thatthe closure member need only substantially seal the exit of theaerosol-forming chamber. The inlet of the aerosol-forming chamber mayremain open, even when the closure member is in the closed position.

The closure member may have any suitable size and shape. The closuremember may be manually operable by a user. Alternatively, the closuremember may be electrically operable, either on user instruction orautomatically.

The closure member may include capillary material. The capillarymaterial may be provided on part or all of the upstream surface of theclosure member. The capillary material will retain any liquid whichcollects on the closure member. This reduces the likelihood thatcondensed liquid will leak from the aerosol generating system. Thecapillary material may comprise any suitable material or combination ofmaterials which is able to retain the collected liquid. The particularpreferred material or materials will depend on the physical propertiesof the liquid aerosol-forming substrate. Examples of suitable materialsare a sponge or foam material, ceramic- or graphite-based materials inthe form of fibres or sintered powders, a foamed metal or plasticsmaterial, a fibrous material, for example made of spinned or extrudedfibres, such as cellulose acetate, polyester, or bonded polyolefin,polyethylene, terylene or polypropylene fibres, nylon fibres or ceramic.

If the aerosol generating system includes a liquid storage portion or acapillary wick or both a liquid storage portion and a capillary wick,the capillary material on the closure member may return liquid dropletsto the liquid storage portion or capillary wick. The capillary materialon the closure member may be in contact with the capillary wick when theaerosol generating system is not in use. The capillary material on theclosure member and the capillary wick may comprise the same material ordifferent materials.

The aerosol generating system may further comprise a liquid storageportion for storing the liquid aerosol-forming substrate.

An advantage of providing a liquid storage portion is that the liquid inthe liquid storage portion is protected from ambient air (because aircannot generally enter the liquid storage portion) and, in someembodiments light, so that the risk of degradation of the liquid issignificantly reduced. Moreover, a high level of hygiene can bemaintained. The liquid storage portion may not be refillable. Thus, whenthe liquid in the liquid storage portion has been used up, the aerosolgenerating system is replaced. Alternatively, the liquid storage portionmay be refillable. In that case, the aerosol generating system may bereplaced after a certain number of refills of the liquid storageportion. Preferably, the liquid storage portion is arranged to holdliquid for a pre-determined number of puffs.

The aerosol generating system may further comprise a capillary wick forconveying the liquid aerosol-forming substrate by capillary action.

Preferably, the capillary wick is arranged to be in contact with liquidin the liquid storage portion. Preferably, the capillary wick extendsinto the liquid storage portion. In that case, in use, liquid istransferred from the liquid storage portion by capillary action in thecapillary wick. In one embodiment, liquid in one end of the capillarywick is vaporized to form a supersaturated vapour. The supersaturatedvapour is mixed with and carried in the air flow. During the flow, thevapour condenses to form the aerosol and the aerosol is carried towardsthe mouth of a user. The liquid aerosol-forming substrate has physicalproperties, including surface tension and viscosity, which allow theliquid to be transported through the capillary wick by capillary action.

The capillary wick may have a fibrous or spongy structure. The capillarywick preferably comprises a bundle of capillaries. For example, thecapillary wick may comprise a plurality of fibres or threads or otherfine bore tubes. The fibres or threads may be generally aligned in thelongitudinal direction of the aerosol generating system. Alternatively,the capillary wick may comprise sponge-like or foam-like material formedinto a rod shape. The rod shape may extend along the longitudinaldirection of the aerosol generating system. The structure of the wickforms a plurality of small bores or tubes, through which the liquid canbe transported by capillary action. The capillary wick may comprise anysuitable material or combination of materials. Examples of suitablematerials are capillary materials, for example a sponge or foammaterial, ceramic- or graphite-based materials in the form of fibres orsintered powders, foamed metal or plastics material, a fibrous material,for example made of spinned or extruded fibres, such as celluloseacetate, polyester, or bonded polyolefin, polyethylene, terylene orpolypropylene fibres, nylon fibres or ceramic. The capillary wick mayhave any suitable capillarity and porosity so as to be used withdifferent liquid physical properties. The liquid has physicalproperties, including but not limited to viscosity, surface tension,density, thermal conductivity, boiling point and vapour pressure, whichallow the liquid to be transported through the capillary device bycapillary action.

The aerosol generating system may be electrically operated. Theelectrically operated aerosol generating system may further comprise anelectric heater for heating the liquid aerosol-forming substrate.

The electric heater may comprise a single heating element.Alternatively, the electric heater may comprise more than one heatingelement for example two, or three, or four, or five, or six or moreheating elements. The heating element or heating elements may bearranged appropriately so as to most effectively heat theaerosol-forming substrate.

The at least one electric heating element preferably comprises anelectrically resistive material. Suitable electrically resistivematerials include but are not limited to: semiconductors such as dopedceramics, electrically “conductive” ceramics (such as, for example,molybdenum disilicide), carbon, graphite, metals, metal alloys andcomposite materials made of a ceramic material and a metallic material.Such composite materials may comprise doped or undoped ceramics.Examples of suitable doped ceramics include doped silicon carbides.Examples of suitable metals include titanium, zirconium, tantalum andmetals from the platinum group. Examples of suitable metal alloysinclude stainless steel, Constantan, nickel-, cobalt-, chromium-,aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-,tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containingalloys, and super-alloys based on nickel, iron, cobalt, stainless steel,Timetal®, iron-aluminium based alloys and iron-manganese-aluminium basedalloys. Timetal® is a registered trade mark of Titanium MetalsCorporation, 1999 Broadway Suite 4300, Denver Colo. In compositematerials, the electrically resistive material may optionally beembedded in, encapsulated or coated with an insulating material orvice-versa, depending on the kinetics of energy transfer and theexternal physicochemical properties required. The heating element maycomprise a metallic etched foil insulated between two layers of an inertmaterial. In that case, the inert material may comprise Kapton®,all-polyimide or mica foil. Kapton® is a registered trade mark of E.I.du Pont de Nemours and Company, 1007 Market Street, Wilmington, Del.19898, United States of America.

Alternatively, the at least one electric heating element may comprise aninfra-red heating element, a photonic source or an inductive heatingelement.

The at least one electric heating element may take any suitable form.For example, the at least one electric heating element may take the formof a heating blade. Alternatively, the at least one electric heatingelement may take the form of a casing or substrate having differentelectro-conductive portions, or an electrically resistive metallic tube.The liquid storage portion may incorporate a disposable heating element.Alternatively, one or more heating needles or rods that run through theliquid aerosol-forming substrate may also be suitable. Alternatively,the at least one electric heating element may be a disk (end) heater ora combination of a disk heater with heating needles or rods.Alternatively, the at least one electric heating element may comprise aflexible sheet of material. Other alternatives include a heating wire orfilament, for example a Ni—Cr, platinum, tungsten or alloy wire, or aheating plate. Optionally, the heating element may be deposited in or ona rigid carrier material.

The at least one electric heating element may comprise a heat sink, orheat reservoir comprising a material capable of absorbing and storingheat and subsequently releasing the heat over time to heat theaerosol-forming substrate. The heat sink may be formed of any suitablematerial, such as a suitable metal or ceramic material. Preferably, thematerial has a high heat capacity (sensible heat storage material), oris a material capable of absorbing and subsequently releasing heat via areversible process, such as a high temperature phase change. Suitablesensible heat storage materials include silica gel, alumina, carbon,glass mat, glass fibre, minerals, a metal or alloy such as aluminium,silver or lead, and a cellulose material such as paper. Other suitablematerials which release heat via a reversible phase change includeparaffin, sodium acetate, naphthalene, wax, polyethylene oxide, a metal,metal salt, a mixture of eutectic salts or an alloy.

The heat sink or heat reservoir may be arranged such that it is directlyin contact with the liquid aerosol-forming substrate and can transferthe stored heat directly to the substrate. Alternatively, the heatstored in the heat sink or heat reservoir may be transferred to theaerosol-forming substrate by means of a heat conductor, such as ametallic tube.

The at least one heating element may heat the aerosol-forming substrateby means of conduction. The heating element may be at least partially incontact with the substrate. Alternatively, the heat from the heatingelement may be conducted to the substrate by means of a heat conductiveelement.

Alternatively, the at least one heating element may transfer heat to theincoming ambient air that is drawn through the aerosol generating systemduring use, which in turn heats the aerosol-forming substrate byconvection. The ambient air may be heated before passing through theaerosol-forming substrate. Alternatively, the ambient air may be firstdrawn through the liquid substrate and then heated.

In one preferred embodiment, the aerosol generating system comprises anelectric heater, a capillary wick and a liquid storage portion. In thatembodiment, preferably the capillary wick is arranged to be in contactwith liquid in the liquid storage portion. In use, liquid is transferredfrom the liquid storage portion towards the electric heater by capillaryaction in the capillary wick. In one embodiment, the capillary wick hasa first end and a second end, the first end extending into the liquidstorage portion for contact with liquid therein and the electric heaterbeing arranged to heat liquid in the second end. When the heater isactivated, the liquid at the second end of the capillary wick isvaporized by the heater to form the supersaturated vapour. Thesupersaturated vapour is mixed with and carried in the air flow. Duringthe flow, the vapour condenses to form the aerosol and the aerosol iscarried towards the mouth of a user.

As discussed above, the capillary wick may comprise any suitablematerial. The capillary properties of the wick, combined with theproperties of the liquid, ensure that the wick is always wet in theheating area. If the wick is dry, there may be overheating, which canlead to thermal degradation of liquid.

The capillary wick and the heater, and optionally the liquid storageportion, may be removable from the aerosol generating system as a singlecomponent.

The aerosol generating system may comprise at least one air inlet. Theaerosol generating system may comprise at least one air outlet. Theaerosol-forming chamber is located between the air inlet and air outletso as to define an air flow route from the air inlet to the air outletvia the aerosol-forming chamber, so as to convey the aerosol to the airoutlet and into the mouth of a user.

The aerosol generating system may be electrically operated and mayfurther comprise an electric power supply. The aerosol generating systemmay further comprise electric circuitry. In one embodiment, the electriccircuitry comprises a sensor to detect air flow indicative of a usertaking a puff. In that case, preferably, the electric circuitry isarranged to provide an electric current pulse to the electric heaterwhen the sensor senses a user taking a puff. Preferably, the time-periodof the electric current pulse is pre-set, depending on the amount ofliquid desired to be vaporized. The electric circuitry is preferablyprogrammable for this purpose. Alternatively, the electric circuitry maycomprise a manually operable switch for a user to initiate a puff. Thetime-period of the electric current pulse is preferably pre-setdepending on the amount of liquid desired to be vaporized. The electriccircuitry is preferably programmable for this purpose.

Preferably, the aerosol generating system comprises a housing.Preferably, the housing is elongate. If the aerosol generating includesa capillary wick, the longitudinal axis of the capillary wick and thelongitudinal axis of the housing may be substantially parallel. Thehousing may comprise a shell and a mouthpiece. In that case, all thecomponents may be contained in either the shell or the mouthpiece. Inone embodiment, the housing includes a removable insert comprising theliquid storage portion, the capillary wick and the heater. In thatembodiment, those parts of the aerosol generating system may beremovable from the housing as a single component. This may be useful forrefilling or replacing the liquid storage portion, for example.

The housing may comprise any suitable material or combination ofmaterials. Examples of suitable materials include metals, alloys,plastics or composite materials containing one or more of thosematerials, or thermoplastics that are suitable for food orpharmaceutical applications, for example polypropylene,polyetheretherketone (PEEK) and polyethylene. Preferably, the materialis light and non-brittle.

Preferably, the aerosol generating system is portable. The aerosolgenerating system may be a smoking system and may have a size comparableto a conventional cigar or cigarette. The smoking system may have atotal length between approximately 30 mm and approximately 150 mm. Thesmoking system may have an external diameter between approximately 5 mmand approximately 30 mm.

Preferably, the aerosol generating system is an electrically operatedsmoking system.

Features described in relation to one aspect of the invention may beapplicable to another aspect of the invention.

The invention will be further described, by way of example only, withreference to the accompanying drawings, of which:

FIG. 1 shows one example of an aerosol generating system having a liquidstorage portion;

FIG. 2 shows an enlarged view of the mouthpiece end of an aerosolgenerating system similar to that shown in FIG. 1;

FIG. 3 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a first embodiment of the invention;

FIG. 4 is a cross sectional view along line IV-IV of FIG. 3;

FIG. 5 shows an enlarged view of the mouthpiece end of an alternativeaerosol generating system according to the first embodiment of theinvention;

FIG. 6 is a cross sectional view along line VI-VI of FIG. 5;

FIG. 7 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a second embodiment of the invention;

FIG. 8 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a third embodiment of the invention; and

FIG. 9 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a fourth embodiment of the invention.

FIG. 1 shows one example of an aerosol generating system having a liquidstorage portion. In FIG. 1, the system is an electrically operatedsmoking system. The smoking system 100 of FIG. 1 comprises a housing 101having a first end which is the mouthpiece end 103 and a second endwhich is the body end 105. In the body end, there is provided anelectric power supply in the form of battery 107 and electric circuitryin the form of hardware 109 and puff detection system 111. In themouthpiece end, there is provided a liquid storage portion in the formof cartridge 113 containing liquid 115, a capillary wick 117 and aheater 119. Note that the heater is only shown schematically in FIG. 1.In the exemplary embodiment shown in FIG. 1, one end of capillary wick117 extends into cartridge 113 and the other end of capillary wick 117is surrounded by the heater 119. The heater is connected to the electriccircuitry via connections 121, which may pass along the outside ofcartridge 113 (not shown in FIG. 1). The housing 101 also includes anair inlet 123, an air outlet 125 at the mouthpiece end, and anaerosol-forming chamber 127.

In use, operation is as follows. Liquid 115 is conveyed by capillaryaction from the cartridge 113 from the end of the wick 117 which extendsinto the cartridge to the other end of the wick which is surrounded byheater 119. When a user draws on the aerosol generating system at theair outlet 125, ambient air is drawn through air inlet 123. In thearrangement shown in FIG. 1, the puff detection system 111 senses thepuff and activates the heater 119. The battery 107 supplies electricalenergy to the heater 119 to heat the end of the wick 117 surrounded bythe heater. The liquid in that end of the wick 117 is vaporized by theheater 119 to create a supersaturated vapour. At the same time, theliquid being vaporized is replaced by further liquid moving along thewick 117 by capillary action. (This is sometimes referred to as “pumpingaction”.) The supersaturated vapour created is mixed with and carried inthe air flow from the air inlet 123. In the aerosol-forming chamber 127,the vapour condenses to form an inhalable aerosol, which is carriedtowards the outlet 125 and into the mouth of the user.

In the embodiment shown in FIG. 1, the hardware 109 and puff detectionsystem 111 are preferably programmable. The hardware 109 and puffdetection system 111 can be used to manage the aerosol generating systemoperation.

FIG. 1 shows one example of an aerosol generating system according tothe present invention. Many other examples are possible, however. Theaerosol generating system simply needs to include leakage preventionmeans (to be described below with reference to FIGS. 2 to 9) configuredto prevent or reduce leakage of liquid aerosol condensate from theaerosol generating system. For example, the system need not beelectrically operated. For example, the system need not be a smokingsystem. In addition, the system may not include a heater, in which caseanother device may be included to vaporize the liquid aerosol-formingsubstrate. For example, a puff detection system need not be provided.Instead, the system could operate by manual activation, for example theuser operating a switch when a puff is taken. For example, the overallshape and size of the housing could be altered. Moreover, the system maynot include a capillary wick. In that case, the system may includeanother mechanism for delivering liquid for vaporization.

However, in a preferred embodiment, the system does include a liquidstorage portion and a capillary wick for conveying the liquid from theliquid storage portion. The capillary wick can be made from a variety ofporous or capillary materials and preferably has a known, pre-definedcapillarity. Examples include ceramic- or graphite-based materials inthe form of fibres or sintered powders. Wicks of different porositiescan be used to accommodate different liquid physical properties such asviscosity and surface tension. The wick must be suitable so that therequired amount of liquid can be delivered to the heater.

As discussed above, according to the invention, the aerosol generatingsystem includes leakage prevention means configured to prevent or reduceleakage of condensed liquid from the aerosol generating system. A numberof embodiments of the invention, including the leakage prevention means,will now be described with reference to FIGS. 2 to 9. The embodimentsare based on the example shown in FIG. 1, although are applicable toother embodiments of aerosol generating systems. Note that FIG. 1 andthe following FIGS. 2 to 9 are schematic in nature. In particular, thecomponents shown are not to scale either individually or relative to oneanother.

FIG. 2 shows an enlarged view of the mouthpiece end of an aerosolgenerating system similar to that of FIG. 1. FIG. 2 only shows themouthpiece end 103 including the aerosol-forming chamber 127 and the airoutlet 125. Other components are not shown in FIG. 2 for clarity.

In FIG. 2, the air flow is shown schematically by arrows 201. It can beseen that liquid droplets (shown schematically at 203) tend to condenseon the inside walls of the aerosol-forming chamber 127, particularlytowards the air outlet 125. Such liquid droplets may be formed as thevapour condenses to form the aerosol. If the airflow does not carry allthe droplets out of the outlet 125 and into the mouth of the user,droplets, particularly the larger droplets, may accumulate on the insidewalls of the aerosol-forming chamber 127, as shown in FIG. 2. Thecondensate droplets 203 may run out of the outlet 125, causing theaerosol generating system to become wet or sticky. This willinconvenience the user.

FIG. 3 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a first embodiment of the invention. FIG.4 is a cross sectional view along line IV-IV of FIG. 3. FIG. 3 shows themouthpiece end 103 including the aerosol-forming chamber 127 and the airoutlet 125. Other components are not shown in FIG. 3, for clarity. InFIG. 3, the air flow is shown schematically by arrows 301 and liquiddroplets 303 are shown accumulating on the inside walls of theaerosol-forming chamber 127.

In the embodiment shown in FIGS. 3 and 4, the inside walls of theaerosol-forming chamber 127 are provided with droplet collectingcavities or recesses 305, 307. The two cavities 305, 307 are provided onopposite sides of the air outlet 125. In the embodiment shown in FIGS. 3and 4, upper cavity 305 is in the form of a substantially cylindricalcavity. As seen in FIG. 4, the cavity 305 has a substantially circularcross section. The cavity 305 is a blind hole. That is to say, thecavity 305 does not extend to the outside of the aerosol generatingsystem. Similarly, in the embodiment shown in FIGS. 3 and 4, lowercavity 307 is also in the form of a substantially cylindrical cavitywith a substantially circular cross section. The cavity 307 is also ablind hole, not extending to the outside of the aerosol generatingsystem.

The cavities 305, 307 act as leakage prevention means. They collectliquid condensate droplets 303 which have accumulated on the insidewalls of the aerosol-forming chamber 127. The cavities 305, 307 arepositioned so as to interrupt the flow route for liquid droplets 303running towards the air outlet. Thus, the liquid droplets are preventedfrom leaking out of the air outlet of the aerosol generating system.

In FIGS. 3 and 4, the cavities are substantially cylindrical with asubstantially circular cross section. However, the cavities may have anysuitable cross section and shape. The cavities may have any suitablediameter. In FIGS. 3 and 4, the cross sectional dimension of the aerosolgenerating system at the air outlet end is shown as W and the crosssectional dimension of the air outlet itself is shown as w. W and w mayhave any suitable values. For example, W may be between 5 mm and 30 mmwhich is the typical range of diameters of cigarettes and cigars. Thecross sectional width w of the air outlet may be determined by severalfactors. If w is relatively small (for example, 1 to 2 mm), the aerosolpassing through the air outlet is concentrated (that is to say, has anincreased density) so that condensation may be increased. This mayincrease the droplet or particle size of the aerosol. In addition, arelatively small w increases the resistance to draw (RTD) and may causeincreased turbulence of the airflow in the housing. This will alsoaffect the aerosol particle size. On the other hand, a relatively largecross sectional width w increases the diffusion angle of the aerosol.This may also affect the aerosol properties. However, a relatively largew may also help to prevent leakage of condensation. The cross sectionalwidths w and W may be varied in proportion to one another. For example,a small W with a relatively large w or a large W with a relatively smallw, may affect the aerosol properties. Preferably, the cross sectionalwidth w of the air outlet is between 1 mm and 5 mm.

In FIGS. 3 and 4, the cavities 305, 307 are shown with a cross sectionaldimension x. Dimension x is preferably 0.5 mm or 1 mm or between 0.5 mmand 1 mm. This size has been found to be advantageous since it is largeenough to collect a sufficient amount of liquid, but small enough totrap the liquid in the cavity by capillary action, even if the aerosolgenerating system is rotated or vertically aligned. The dimension x maybe chosen depending on the physical properties of the liquidaerosol-forming substrate and need not be equal for the two cavities.

The cavities may also have any suitable length l. For example, thelength l of the cavities may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm or even asmuch as 1 cm. The length l may be chosen so that the cavities cancollect a sufficient amount of liquid. The length l may be chosendepending on the physical properties of the liquid aerosol-formingsubstrate. The length of the two cavities need not be equal. Thecavities may not have the same length l across their entire crosssection. For example, the cavities may be asymmetric.

In FIGS. 3 and 4, the cavities 305, 307 are shown positioned at a crosssectional distance a from the exterior of the aerosol generating system.Distance a can be chosen to have any value and may not be equal for thetwo cavities. Similarly, the cavities 305, 307 are shown positioned at across sectional distance b from the air outlet 125 of the aerosolgenerating system. Distance b can be chosen to have any value and maynot be equal for the two cavities. All the dimensions may be chosen asdesired, depending on, for example, the desired size for the aerosolgenerating system and the physical properties of the liquidaerosol-forming substrate.

In FIGS. 3 and 4, the cavities are located close to the air outlet. Thismay be preferable, because this location has been found to be mosteffective for collecting the liquid droplets. This is because air flowin the aerosol generating system may have a tendency to push the liquiddroplets towards the air outlet. However, the cavities may be locatedelsewhere in the aerosol-forming chamber. In FIGS. 3 and 4, two cavitiesare provided, one either side of the air outlet. However, any suitablenumber of cavities, including a single cavity, may be provided. Forexample, more than two cavities may be provided and these may bearranged substantially in a circle around, for example concentric with,the air outlet 125. The cavities may be linked to one another. Thecavities may also be connected to the capillary wick, for example viaone or more return passageways. This will allow the liquid collecting inthe cavities to be recycled. Other variations are possible.

FIG. 5 shows an enlarged view of the mouthpiece end of an alternativeaerosol generating system according to the first embodiment of theinvention. FIG. 6 is a cross sectional view along line VI-VI of FIG. 5.FIG. 5 shows the mouthpiece end 103 including the aerosol-formingchamber 127 and the air outlet 125. Other components are not shown inFIG. 5, for clarity. In FIG. 5, the air flow is shown schematically byarrows 501 and liquid droplets 503 are shown accumulating on the insidewalls of the aerosol-forming chamber 127.

In the embodiment shown in FIGS. 5 and 6, the inside walls of theaerosol-forming chamber are provided with a single droplet collectingcavity or recess 505. As seen in FIG. 6, the cavity 505 is in the formof a substantially annular groove surrounding air outlet 125. As withcavities 305 and 307 in FIGS. 3 and 4, the cavity 505 is a blind cavity.That is to say, the cavity 505 does not extend to the outside of theaerosol generating system.

The cavity 505 acts as leakage prevention means. The cavity 505 collectsliquid condensate droplets 503 which have accumulated on the insidewalls of the aerosol-forming chamber 127. The cavity 505 is positionedso as to interrupt the flow route for liquid droplets 503 runningtowards the air outlet. Thus, the liquid droplets are prevented fromleaking out of the air outlet of the aerosol generating system.

In FIGS. 5 and 6, the cavity is in the form of a circular annulargroove. However, the cavity may have any suitable cross section andshape. As in FIGS. 3 and 4, in FIGS. 5 and 6, the cross sectionaldimension of the aerosol generating system at the air outlet end isshown as Wand the cross sectional dimension of the air outlet itself isshown as w. Wand w may have any suitable values as discussed above. Forexample, W may be between 5 mm and 30 mm and w may be between 1 mm and 5mm.

In FIGS. 5 and 6, the cavity 505 is shown with an annular crosssectional width y. Width y is the difference between the radius of theouter circle forming the annulus and the radius of the inner circleforming the annulus. Dimension y is preferably 0.5 mm or 1 mm or between0.5 mm and 1 mm. This size has been found to be advantageous since it islarge enough to collect a sufficient amount of liquid, but small enoughto trap the liquid in the cavity by capillary action, even if theaerosol generating system is rotated or vertically aligned. Thedimension y may be chosen depending on the physical properties of theliquid aerosol-forming substrate.

The cavity may also have any suitable depth d. For example, the depth dof the cavity may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm or even as much as 1cm. The depth d may be chosen so that the cavity 505 can collect asufficient amount of liquid. The depth d may be chosen depending on thephysical properties of the liquid aerosol-forming substrate. The cavitymay not have the same depth d across the entire cross section.

In FIGS. 5 and 6, the cavity 505 is shown positioned at a crosssectional distance c from the outside of the aerosol generating system.That is to say, the distance from the outer circle forming the annulusand the exterior of the aerosol generating system is c. Distance c canbe chosen to have any value. Similarly, the cavity 505 is shownpositioned at a cross sectional distance d from the air outlet 125 ofthe aerosol generating system. Distance d can be chosen to have anyvalue. In FIGS. 5 and 6, the cavity is symmetrically located around theair outlet. However, this need not be the case and the annular cavitymay, instead, be off-centre. All the dimensions can be chosen asdesired, depending on, for example, the desired size for the aerosolgenerating system and the physical properties of the liquidaerosol-forming substrate.

In FIGS. 5 and 6, the annular cavity is located close to the air outlet.This may be preferable, because this location has been found to be mosteffective for collecting the liquid droplets. This is because air flowin the aerosol generating system may have a tendency to push the liquiddroplets towards the air outlet. However, the cavity may be locatedelsewhere in the aerosol-forming chamber. In addition, severalconcentric grooves may be provided. The cavity may also be connected tothe capillary wick, for example via one or more return passageways. Thiswill allow the liquid collecting in the cavities to be recycled. Othervariations are possible.

In the embodiments shown in FIGS. 3, 4, 5 and 6, the cavity or cavitiesmay contain capillary material. The cavity or cavities may besubstantially filled with capillary material. The capillary material inthe cavity is arranged to hold the liquid condensate collecting in thecavity. In that way, the amount of free liquid, that is to say, liquidwhich is free to flow, is reduced. Providing such capillary materialfurther reduces the likelihood that condensed liquid will leak from theaerosol generating system. The capillary material may extend out of thecavity and connect to the capillary wick. For example, the capillarymaterial may extend through a return passageway. This allows condensedliquid to be recycled.

The capillary material may comprise any material which is suitable forretaining the liquid. Examples of suitable materials are a sponge orfoam material, a foamed metal or plastics material, a fibrous material,for example made of spinned or extruded fibres, such as celluloseacetate, polyester, or bonded polyolefin, polyethylene, terylene orpolypropylene fibres, nylon fibres or ceramic.

Thus, in the embodiments shown in FIGS. 3, 4, 5 and 6, leakageprevention means are provided in the form of one or more liquidcollecting cavities. The cavity or cavities allow condensed liquiddroplets to be collected, thereby preventing leakage from the aerosolgenerating system. Optionally, the collected liquid may be recycled backto the capillary wick, thereby reducing wastage.

FIG. 7 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a second embodiment of the invention.FIG. 7 shows the mouthpiece end 103 including the cartridge 113, thecapillary wick 117, the heater 119, the aerosol-forming chamber 127 andthe air outlet 125. Other components are not shown in FIG. 7 forclarity.

In FIG. 7, air flow is shown schematically by arrows 701. It can be seenthat air flow is directed across the capillary wick and heater in asubstantially perpendicular direction. That is to say, the air flow issubstantially perpendicular to the longitudinal axis of the housing andthe capillary wick. In FIG. 7, one inside wall of the housing isprovided with a hooked member 705. The hooked member 705 has a hook 705a at its end furthest from the capillary wick and a sloped portion 705 bat its end nearest to the capillary wick. Liquid droplets 703 are shownaccumulating on the inside of the hooked member 705 between thecapillary wick 117 and heater 119 and the air outlet 125. The hookedmember 705 acts as leakage prevention means. The hooked member 705collects, in the hook 705 a, condensed liquid droplets which wouldotherwise collect on the inside walls. The hook 705 a prevents theliquid droplets from flowing further downstream. The hooked member 705provides a recycle path in the form of sloped portion 705 b to channelthe collected liquid droplets back to the capillary wick.

In FIG. 7, the air flow is shown directed in a direction substantiallyperpendicular to the capillary wick and heater. However, the leakageprevention means in the form of hooked member 705 may still be providedwhen the air flow is not in a direction substantially perpendicular tothe capillary wick and heater. The hooked member is, however,particularly effective in the embodiment of FIG. 7 because the air flowdirection means that there is a tendency for condensed liquid dropletsto form in the region of the hooked member. The hooked member 705 maytake any appropriate form. For example, the hooked member may extendaround all or part of the circumference of the aerosol generatingsystem. The hooked member may extend along any length of the aerosolgenerating system between the capillary wick and heater and the airoutlet. The hooked member may be provided on a wall of theaerosol-forming chamber. More than one hooked member may be provided.

The sloped portion 705 b of the hooked member need not be provided.However, the sloped portion 705 b is advantageous because it assistswith transfer of liquid droplets back to the capillary wick. The slopedportion prevents liquid droplets accumulating between the hook and thecapillary wick. The sloped portion may have any appropriate angle andlength. The hook 705 a of the hooked member collects the liquiddroplets. The hook may have any appropriate shape. The shape of the hookmay depend on the size of condensed liquid droplets expected. This maybe determined by the physical properties of the liquid aerosol-formingsubstrate.

In one variation of the embodiment shown in FIG. 7, the hooked member705 may include capillary material on part or all of its surface. Thatcapillary material is arranged to hold liquid condensate collecting onthe hooked member. In that way, the amount of free liquid, that is tosay, liquid which is free to flow, is reduced. Providing such capillarymaterial further reduces the likelihood that condensed liquid will leakfrom the aerosol generating system. The capillary material assists withthe transfer of the condensed liquid droplets back to the capillarywick. The capillary material may be in contact with the capillary wick.This allows liquid to be recycled.

The capillary material may comprise any material or combination ofmaterials which is suitable for retaining the liquid. Examples ofsuitable materials are a sponge or foam material, a foamed metal orplastics material, a fibrous material, for example made of spinned orextruded fibres, such as cellulose acetate, polyester, or bondedpolyolefin, polyethylene, terylene or polypropylene fibres, nylon fibresor ceramic.

Thus, in the embodiment shown in FIG. 7, leakage prevention means areprovided in the form of a hooked member. The hooked member allows liquiddroplets to be collected thereby preventing leakage of liquid condensatefrom the aerosol generating system. Optionally, the collected liquid maybe recycled back to the capillary wick, thereby reducing wastage.

FIG. 8 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a third embodiment of the invention. FIG.8 shows the mouthpiece end 103 including the cartridge 113, thecapillary wick 117, the heater 119, the aerosol-forming chamber 127 andthe air outlet 125. Other components are not shown in FIG. 8 forclarity. In FIG. 8, air flow is shown schematically by arrows 801.

The aerosol generating system of FIG. 8 further includes an impactor 805positioned on the downstream side of the capillary wick and heater. Theimpactor 805 allows liquid droplets 803 to be trapped on the upstreamside of the impactor. In FIG. 8, impactor 805 includes capillarymaterial 807 on the upstream side although this need not be included. InFIG. 8, the capillary material 807 is in direct contact with capillarywick 117, although this direct contact is optional. The contact allowsany liquid droplets collected by impactor 805 to be transferred back tothe capillary wick.

The impactor 805 acts as leakage prevention means. The impactor collectsliquid droplets, which may otherwise collect on the inside walls. Theimpactor disrupts the airflow in the aerosol generating systemdownstream of the capillary wick and heater. The impactor tends tocollect the larger droplets. Larger droplets may be droplets having adiameter greater than around 1.0 μm. Alternatively, larger droplets maybe droplets having a diameter greater than around 1.5 μm This is becausethe larger droplets have the greatest inertia and are therefore mostlikely to collect on the impactor. Smaller liquid droplets tend to becarried in the air flow diverting around the impactor. But, largerliquid droplets cannot undergo such a diversion around the impactor andthe larger droplets impact on the upstream side of the impactor instead.

If the impactor includes capillary material at least on its upstreamside, the liquid droplets may be more easily retained. In that way, theamount of free liquid, that is to say, liquid which is free to flow, isreduced. Providing such capillary material further reduces thelikelihood that liquid will leak from the aerosol generating system. Ifthe capillary material is in contact with the capillary wick, thisallows collected liquid droplets to be transferred back to the capillarywick. This allows liquid to be recycled.

The impactor 805 may take any appropriate form. For example, theimpactor may have any suitable cross sectional shape and size. Theupstream surface of the impactor, on which capillary material may belocated, may have any suitable shape and size. The size of the upstreamsurface of the impactor will affect the size of liquid droplets whichare collected. A small upstream surface area will allow only the largestdroplets to be collected. A larger upstream surface area will allowsmaller droplets to be collected too. Thus, the size of the upstreamsurface may be chosen depending on the desired aerosol properties andthe physical properties of the liquid aerosol-forming substrate.

If the impactor is provided with capillary material in contact with thecapillary wick, the impactor may be positioned at any suitable distancefrom the heater. The distance from the heater will affect the size ofthe droplets which are collected on the impactor. If the impactor is notprovided with capillary material in contact with the capillary wick, theimpactor may be positioned at any suitable distance from the capillarywick and heater. Preferably, the impactor is supported in theaerosol-forming chamber by one or more struts (not shown in FIG. 8).

In FIG. 8, capillary material is shown on the upstream surface of theimpactor 805. The capillary material may be provided on all or part ofthe upstream surface. Capillary material may additionally oralternatively be provided on other surfaces of the impactor. Thecapillary material may comprise any material or combination of materialswhich is suitable for retaining the liquid. Examples of suitablematerials are a sponge or foam material, a foamed metal or plasticsmaterial, a fibrous material, for example made of spinned or extrudedfibres, such as cellulose acetate, polyester, or bonded polyolefin,polyethylene, terylene or polypropylene fibres, nylon fibres or ceramic.

Thus, in the embodiment shown in FIG. 8, leakage prevention means areprovided in the form of an impactor. The impactor disrupts the air flowthereby allowing liquid droplets to be collected. This prevents or atleast reduces leakage from the aerosol generating system. Optionally,the collected liquid may be recycled back to the capillary wick, therebyreducing wastage.

FIG. 9 shows an enlarged view of the mouthpiece end of an aerosolgenerating system according to a fourth embodiment of the invention.FIG. 9 shows the mouthpiece end 103 including the cartridge 113, thecapillary wick 117, the heater 119, the aerosol-forming chamber 127 andthe air outlet 125. In FIG. 9, the aerosol-forming chamber 127 comprisewalls 127 a and exit 127 b. Other components are not shown in FIG. 9 forclarity. In FIG. 9, air flow is shown schematically by arrows 901.

The aerosol generating system of FIG. 9 further includes a closuremember 905. In this embodiment, closure member comprises a closure plate905 a supported on a shaft 905 b. The closure plate 905 a issubstantially perpendicular to the longitudinal axis of the system. Theshaft 905 b is substantially parallel to the longitudinal axis of thesystem. The shaft 905 b is supported inside the aerosol generatingsystem by one or more struts 905 c. In FIG. 9, the closure member 905 isshown in the open position. As shown by arrow 907, closure member can bemoved towards the aerosol-forming chamber into a closed position.

The closure member 905 acts as leakage prevention means. When theaerosol generating system is in use, the closure member 905 is in theopen position (as shown in FIG. 9). An air flow route is providedbetween the air inlet and the air outlet via the aerosol-formingchamber. The air flows through the aerosol-forming chamber exit 127 band diverts around the closure plate 905 a as shown by the arrows 901.When the aerosol generating system is not in use, the closure member 905may be moved to the closed position (not shown). In the closed position,the closure plate 905 a abuts the walls 127 a of the aerosol-formingchamber, thereby sealing the aerosol-forming chamber. Any liquiddroplets condensing on the inside walls of the aerosol-forming chamberare unable to leak out of the aerosol generating system because the exit127 b is sealed. This is particularly useful, because the aerosolgenerating system will cool after use and any aerosol remaining in theaerosol-forming chamber will begin to condense into liquid droplets.

The closure member 905 may be manually operated by a user. For example,the shaft 905 b may be threaded and may cooperate with a threaded nut(not shown). As the user rotates the closure member in one direction,the closure member will move towards the aerosol-forming chamber andinto the closed position. As the user rotates the closure member in theopposite direction, the closure member will move away from theaerosol-forming chamber and into the open position. Thus, the user canset the closure member to the open position before using the aerosolgenerating system and can set the closure member to the closed positionafter use.

Alternatively, the closure member 905 may be electrically operated.Again, the shaft 905 b may be threaded and may cooperate with a threadednut (not shown). For example, when the user is about to use the aerosolgenerating system, the user may move a switch (not shown) into an “on”position. Then, electric circuitry may activate an actuator, for examplea motor or an electromagnetic actuator, to move the closure member 905into the open position. Then, after use, the user can move the switch(not shown) into an “off” position. Then, the electric circuitry mayactivate the motor to move the closure member into the closed position.Alternatively, the electric circuitry may automatically activate themotor to move the closure member into the closed position. For example,the electric circuitry may be arranged to monitor the time since thelast puff. If that time reaches a predetermined threshold, this willindicate that the user has finished using the aerosol generating system.Then, the electric circuitry can activate the motor to move the closuremember into the closed position.

The closure member may take any appropriate form. For example, theclosure plate may have any suitable surface area as long as it is ableto substantially seal the exit of the aerosol-forming chamber. Asalready mentioned, the shaft 905 b may be threaded and may cooperatewith a threaded nut. Alternative means for moving the closure memberbetween the closed and open positions may be provided.

The position of the closure member in the open position (as shown inFIG. 9) means that the closure plate 905 a may act as an impactor likethat shown in FIG. 8. This will depend upon the distance of the closureplate 905 a from the capillary wick and heater when the closure memberis in the open position. Thus, the closure member 905 may have dualfunctionality. The closure plate 905 a may be provided with capillarymaterial on some or all of its upstream surface. This will allow anyliquid droplets which are collected by the closure plate 905 a to beretained and will minimise the amount of free liquid. The capillarymaterial may provide a return path for the collected liquid droplets.For example, when the closure member is in the closed position, thecapillary material on the plate 905 a may contact capillary material onthe inside of the walls 127 a of the aerosol-forming chamber, therebyallowing liquid to be channelled back towards the capillary wick. Thecapillary material may comprise any material or combination of materialswhich is suitable for retaining the liquid. Examples of suitablematerials are a sponge or foam material, a foamed metal or plasticsmaterial, a fibrous material, for example made of spinned or extrudedfibres, such as cellulose acetate, polyester, or bonded polyolefin,polyethylene, terylene or polypropylene fibres, nylon fibres or ceramic.

Thus, in the embodiment shown in FIG. 9, leakage prevention means areprovided in the form of a closure member. The closure member allows theaerosol-forming chamber to be substantially sealed when the aerosolgenerating system is not in use. This prevents liquid droplets leakingout of the aerosol generating system. Optionally, any liquid whichcollects on the closure member may be recycled back to the capillarywick, thereby reducing wastage.

In the above embodiments, capillary material may be provided inconjunction with the leakage prevention means. However, the capillarymaterial may, in fact, be provided alone to act as leakage preventionmeans in its own right. The capillary material may comprise any materialor combination of materials which is suitable for retaining the liquid.Examples of suitable materials are a sponge or foam material, a foamedmetal or plastics material, a fibrous material, for example made ofspinned or extruded fibres, such as cellulose acetate, polyester, orbonded polyolefin, polyethylene, terylene or polypropylene fibres, nylonfibres or ceramic.

Thus, according to the invention, the aerosol generating system includesleakage prevention means for preventing or reducing leakage of condensedliquid from the aerosol generating system. Embodiments of the leakageprevention means have been described with reference to FIGS. 2 to 9.Features described in relation to one embodiment may also be applicableto another embodiment. For example, the aerosol generating system may beprovided with leakage prevention means according to one embodiment aswell as leakage prevention means according to another embodiment.

1.-12. (canceled)
 13. An aerosol generating system for heating a liquidaerosol-forming substrate, the system comprising: an aerosol-formingchamber; and leakage prevention means configured to prevent or reduceleakage of liquid aerosol condensate from the aerosol generating system,wherein, the leakage prevention means comprises at least one cavity in awall of the aerosol-forming chamber, for collecting liquid condensateformed from the aerosol-forming substrate and the cavity has across-sectional dimension x, where x is preferably 0.5 mm or 1 mm orbetween 0.5 mm and 1 mm.
 14. The aerosol generating system according toclaim 13, wherein the leakage prevention means comprises at least onecavity in a wall of the aerosol-forming chamber, for collecting liquidcondensate formed from the aerosol-forming substrate.
 15. The aerosolgenerating system according to claim 14, wherein the at least one cavitycontains capillary material.
 16. The aerosol generating system accordingto claim 13, wherein the leakage prevention means comprises at least onehooked member for collecting droplets of liquid condensate formed fromthe aerosol-forming substrate.
 17. The aerosol generating systemaccording to claim 16, wherein the at least one hooked member comprisesa recycle path for recycling the collected droplets of the liquidcondensate formed from the aerosol-forming substrate.
 18. The aerosolgenerating system according to claim 16, wherein the at least one hookedmember includes capillary material.
 19. The aerosol generating systemaccording to claim 13, wherein the leakage prevention means comprises animpactor for disrupting airflow in the aerosol-forming chamber so as tocollect droplets of liquid being formed from the aerosol-formingsubstrate.
 20. The aerosol generating system according to claim 19,wherein the impactor includes capillary material.
 21. The aerosolgenerating system according to claim 13, wherein the leakage preventionmeans comprises a closure member for substantially sealing theaerosol-forming chamber when the aerosol generating system is not inuse.
 22. The aerosol generating system according to claim 13, furthercomprising a liquid storage portion for storing the liquidaerosol-forming substrate.
 23. The aerosol generating system accordingto claim 13, further comprising a capillary wick for conveying theliquid aerosol-forming substrate by capillary action.
 24. The aerosolgenerating system according to claim 13, wherein the aerosol generatingsystem is electrically operated and further comprises an electric heaterfor heating the liquid aerosol-forming substrate.